Cannabis Use Disorder Emergency Department Visits and Hospitalizations and 5-Year Mortality.

Importance: Cannabis use disorders (CUD) are associated with adverse health effects, including mental disorders and motor vehicle collision-related injuries. However, little is known about whether CUDs are associated with increased mortality risk. Objective: To examine whether individuals receiving incident hospital-based care (an emergency department visit or hospitalization) for a CUD is associated with increased risk of death. Design, Setting, and Participants: This population-based retrospective cohort study included all individuals aged 15 to 105 years living in Ontario, Canada, between 2006 and 2021 (n = 11 622 571 individuals). Overall and cause-specific mortality were compared between individuals with incident hospital-based CUD care and age- and sex-matched members of the general population or individuals with hospital-based care for other substance use disorders using cause-specific hazard models adjusted for comorbid mental health, substance use, and chronic health conditions. Statistical analysis was performed from September to December 2024. Exposure: Incident hospital-based CUD care. Main Outcomes and Measures: Overall and cause-specific mortality identified using vital statistics. Results: The matched analysis included 527 972 individuals (mean [SD] age, 29.9 [13.6] years; 330 034 [62.5%] female) with a median (IQR) follow-up of 5 (3-9) years; 106 994 had incident CUD. Within 5 years of incident hospital-based CUD care, 3770 individuals (3.5%) died compared with 3770 (0.6%) of matched general population members. After adjusting for comorbid conditions, individuals with incident hospital-based CUD care were at increased risk of death relative to the general population (adjusted hazard ratio [aHR], 2.79 [95% CI, 2.62-2.97]). Individuals with hospital-based CUD care were at increased risk of all investigated types of death and particularly elevated risk of death by suicide (aHR, 9.70 [95% CI, 6.04-15.57]), trauma (aHR, 4.55 [95% CI, 3.55-5.82]), opioid poisoning (aHR, 5.03 [95% CI, 2.86-8.84]), other drug poisonings (aHR, 4.56 [95% CI, 3.11-6.68]), and lung cancer (aHR, 3.81 [95% CI, 2.39-6.07]) relative to the general population. Compared with an individual with hospital-based care for CUD, individuals with hospital-based care for alcohol (aHR, 1.30 [95% CI, 1.26-1.34]), stimulants (aHR, 1.69 [95% CI, 1.62-1.75]), and opioids (aHR, 2.19 [95% CI, 2.10-2.27]) were at relatively increased risk of death within 5 years. Conclusions and Relevance: In this cohort study of all residents of Ontario, Canada, individuals with incident hospital-based CUD care were at markedly increased risk of death compared with the general population. These findings suggest important clinical and policy implications, given global trends toward cannabis legalization and market commercialization accompanied by increasing cannabis use and CUDs.